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Chiropractic Care and Risk of Vertebrobasilar Stroke - a Case-control Study

Date Posted:30/09/2015
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Chiropractic & Manual Therapies 2015: 23; 19


Kosloff T, Elton D, Tao J & Bannister W


Neck pain and headache (including migraine) are common conditions that lead people to consult a chiropractor. There have been suggestions that associations exist between spinal manipulative therapy (SMT) and stroke in those under the age of 45 years due to damage of the vertebrobasilar artery (VBA).

Studies done by Rothwell, et. al. and Cassidy, et. al. reported an increased risk of VBA stroke in the under 45's visiting a chiropractor. However, the study done by Cassidy, et. al., showed that the statistics were similar in comparison with people visiting a primary care physician and thus, concluded that the relationship between VBA stroke and SMT was non-causal.


The purpose of this study was to replicate that of Cassidy, et. al, it being considered one of the best designed studies into ascertaining any association between VBA stroke and chiropractic manipulative treatment. It also sought to compare the association between recent primary care provision (PCP) care and VBA stroke.

Study Description

Participants were selected using health insurance claims data of people that had had a VBA stroke or stenosis of the VBA and had attended hospital for their condition. The study was done in America, in all states excepting one.

The sample was selected from 2 sources:

a) people with commercial medical insurance: comprising of 1159 VBA stroke cases and 4633 controls. The average age of this sample was 65.1 years and 64.8% were male.

b) people with 'Medicare advantage' insurance: comprising of 670 VBA stroke cases and 2680 controls. The average age of this group was 76.1 years and 58.6% were male.

Separate analysis was done on people under 45 years of age and people over 45 years of age.

Strengths and Weaknesses of Study

Strengths Weaknesses
This was a well-done study                                                  The claims data used does not provide information about what happened in the actual clinical encounter
  The data used did not provide information about other risk factors for VBA stroke, e.g. migraine or recent infection

Outcomes of Study

A large proportion of the population under study had a comorbid condition, for example hypertension, ischaemic heart disease, endocrine issues, disease of the pulmonary circulation, or hypercholesterolaemia.

Visits to chiropractors within 30 days of hospital admission occurred in 1.6% of commercially insured people, compared to 1.3% of controls.

Visits to a PCP within 30 days of hospital admission occurred in 18.9% of commercially insured people, compared to only 6.8% of controls.

No overall association between VBA stroke and chiropractic visits was found in the overall sample. However, there was an association noted between VBA stroke and PCP visits in all age groups.


In spite of what other case-controlled studies have reported, this study found no significant association between exposure to chiropractic and the risk of VBA stroke. The study strengthens the viewpoint that chiropractic care is not a likely cause of VBA strokes.

Glossary of Terms

comorbid: a condition that is present simultaneously with another condition

control: used as a constant, unchanging standard of comparison in a scientific experiment or research project

endocrine: glands that release hormones

hypercholesterolaemia: high levels of cholesterol in the blood

hypertension: high blood pressure

ischaemic: having a compromised blood supply


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